Maech 1, 1S67.] 



HARDWICKE'S SCIENCE-GOSSIP. 



51 



and South African hirundines, as respects the 

 equator (their divisional line oihahitat demarcation). 

 Now swallows, like all migrant birds, regulate their 

 yearly emigrations and immigrations by that conserva- 

 tive instinct which impels them to seek ever for the 

 most genial climate, and to escape from the extremes 

 of the different atmospheric conditions of cold and 

 heat, rain and drought. Now these conditional 

 states of the atmosphere are reversed yearly in 

 Africa, according to the sun's position in the 

 ecliptic ; and the monsoon rains are regulated 

 by the solar declination, according as that 

 luminary is north and south of the equator ; 

 whilst that equatorial belt of perpetual condensa- 

 tion, 300 or 400 miles broad (as described by Captain 

 Maury in his great work on physical phenomena), 

 and which vibrates latitudinally, agreeable to the 

 sun's position, between latitude 5° south and lati- 

 tude 15° north, is ruled by the same influence. 

 What then are these climate repellents, and how do 

 they operate locally, as regards the great African 

 peninsula? Why thus. On April 13th, the sun is 

 yearly vertical to Sierra Leone, Katunga on the 

 Niger, and the southern uplands of Abyssinia ; and 

 what is the result of the sun's declination being then 

 at nine degrees over this belt of Africa, from west 

 to east ? Why, that the deluging monsoon 

 rains, following the sun as they do, inundate the 

 countries south of latitude 9° to the extent of 

 500 miles, and 300 miles to the north thereof — em- 

 bracing thus to the southward, Fernando Po, the 

 Cameron Mountains, the mouths of the Niger River, 

 the Gold, Slave, and Ivory Coasts ; to the west- 

 ward, Sierra Leone, and the Gambia Settlements ; 

 to the northward, the mountain sources of the 

 rivers Gambia and Niger, and the affluents of Lake 

 Tchad, with the vicinity south of Timbuctoo ; and to 

 the eastward, on the other side of Africa, Magadoxo, 

 Afan, Somanli, Gallas, Abyssinia, and Nubia, col- 

 lectively. Now this solar movement regulates all 

 the hirundiues that Jnjbernate north of the equator, 

 and which emigrate yearly to Europe, aud Asia, and 

 the Azores, in April, earlier or later, according as 

 the monsoon rains set in. 



Now what occurs six months afterwards, namely, 

 on 13th October, when the sun having re-crossed 

 the line, and become vertical to those parts or 

 Southern Africa that lie north and south of latitude 

 9° south ? Why this ! The same advancing clima- 

 tic foe (the sun's attendant ever), the deluging rains 

 which drove the swallows to the north, as he moved 

 towards the tropic of Cancer in April, now chases 

 them to the south, when that luminary is moving in 

 October, towards the opposite tropic of Capricorn. 

 And thus the migratory movements of the African 

 hirundiues are reversed geographically; for when 

 the sun is advancing northward in April, the Sene- 

 gambian and Abyssinian swallows seek their tem- 

 perate, food-abounding countries, Europe and Asia, 



for comfort and nidification ; whilst the swallows of 

 the Cape, Natal, and the Mozambique Coast, are 

 driven to the south, for their temperate climate and 

 generative purposes, in October or thereabouts, 

 yearly; which accords, indeed, with Dr. Living- 

 stone's narrative, and the accounts of Le Valliant 

 and other naturalist observers and writers. Now, 

 I have always assumed that the equatorial calm belt 

 of constant precipitation, as referred to above, 

 divides permanently the North African from the 

 South African swallow as to migratory movements, 

 and the periods of moulting and incubation, and all 

 I have read on the subject confirms this my convic- 

 tion ; for, as the climatic conditions of North and 

 South Africa are reversed, so are the animal phe- 

 nomena depending thereon (as it is in India, Aus- 

 tralia, and the two American continents). Whence 

 then were the swallows seen by E. L. Simmouds 

 coming, and whither proceeding, in November, 

 1S65 ? Why — selon moi— they were the hirundiues 

 of Lower Guinea, the same as Dr. Livingstone 

 speaks of in 1855, as seen at Loanda in June (but 

 not those he saw in migratory transit at Kuruma 

 in December, 1852 ; for these last were Cape of 

 Good Hope swallows); and as the SW. monsoon — 

 which blows on the coast of Upper Guinea, and into 

 the Gulf of Guinea— is over about the end of Octo- 

 ber, these birds were returning thither for their 

 winter hybernation, south of the mountains of Kong, 

 as the European swallows do to the north and 

 north-east of that chain, but 500 miles and more to 

 the northward. H. E. Austen, 



Lieutenant -Colonel and M.B.M.S. 

 St. Hclier's, Jersey. 



N.B. — The Abyssinian swallows pass into 

 Eastern Europe, Syria, and Turkey in Asia, in 

 summer ; and the swallows of Lower Guinea 

 oscillate migratorily between Cape Erio in latitude 

 6S° south and latitude 8° north probably. 



APROPOS. 



fTUIE insertion, in the last number of Science 

 -*- Gossip, of an extract from my Monograph of 

 the British Psocida? ("Ent. Month. Mag."), wherein 

 I avow myself a sceptic as to the ability of Atropos 

 to produce an audible sound, following Mr. Chaney's 

 article in which he distinctly claims for the insect 

 the attribute of causing a ticking, induces me to say 

 a few words on the subject. Without wishing to 

 call in question Mr. Chaney's powers of observation, 

 I still think that some error has occurred, and shall 

 remain an unbeliever until I catch Atropos, flagrante 

 delicto. I shall be only too glad if Mr. Chaney 

 will forward to me living examples of the insect vi hich 

 have been seen and heard in the act of "ticking." 

 Having been as a boy brought up in a then wild part 

 i of Essex, which, though actually not twenty miles 



